1. Field of the Invention
The present invention relates to an apparatus and a method for respectively recording digital video and audio signals, and in particular, to an apparatus and a method for respectively recording digital video and audio signals in both end portions and a middle portion of each inclined track of a magnetic tape, such as a helical scan head type digital video tape recorder (referred to as a "digital VTR" hereinafter).
2. Description of the Related Art
FIG. 8 is a timing chart of a signal processing in recording and reproducing a digital audio signal by a conventional D-1 type digital VTR which a 1/2 inch digital VTR for use in broadcasting made based on a standard of the SMPTE (Society of Motion Picture and Television Engineers). In FIG. 8, c represents the input video signal, a1 represents the input time interval of the recording audio signal, a2 represents the recording processing time interval of the digital audio signal, a3-a6 represent the recording time interval of the digital audio signal, b1-b4 represent the reproducing time interval of the digital audio signal, b5 represents the reproducing processing time interval of the digital audio signal, b6 represents the output time interval of the reproducing audio signal, e represents one segment, each f represents one field, and t represents increasing time.
When it is tried as an editing process to execute a cross-fade editing process wherein first video and audio signals are faded in and second video and audio signals are faded out crossing fading-in and fading-out operations, by means of the conventional D-1 type digital VTR with reproducing magnetic heads which are put in advance of recording magnetic heads by 8.5 segments, as shown by d in FIG. 8, any time interval required for the digital audio signal reproducing process cannot be established as shown in b4 of FIG. 8, and therefore the cross-fade editing cannot be executed.
FIG. 14 shows a tape format showing a method of recording digital video and audio signals which is used in the conventional D-1 type digital VTR.
Referring to FIG. 14, reference numeral 100 denotes a recording magnetic tape having a width of 1/2 inch. A cue audio track 101 is formed in the top part of the magnetic tape 100, while a control track 102 and a time code track 103 are formed in the bottom part of the magnetic tape 100. In FIG. 14, a tape running direction 104 and a corresponding head rotation direction 105 are shown.
A digital audio signal 106 is recorded in the middle portion, between two video sectors 107 of each inclined track in the D-1 type digital VTR. In this case, since the boundaries each between respective adjacent fields are placed in the middle portion of each inclined track, namely, the start point and the end point of each field interval is placed in the middle portion of each inclined track, in order to execute, for example, a double speed playback which is defined as a playback operation for reproducing signals recorded in the fields or frames with skipping one field or one frame, it is required to instantaneously move a set of automatic tracking movable magnetic heads (referred to as AT magnetic heads hereinafter) from the end point of the field, which is currently subjected to reproduction located at the middle portion of the inclined track, into the start point of the next reproduction field located at the middle portion of the inclined track separated apart from the current field by a plurality of tracks. In this case, it is extremely difficult to control the AT magnetic heads, and therefore, a measure of providing an increased number of reproducing magnetic heads, or the like must be taken in order to cope with the above-mentioned problems.
Further, FIG. 2 shows a tape format which is used in a conventional D-3 type digital VTR which is a 1/2 inch digital VTR for use in broadcasting made based on a standard of the above-mentioned SMPTE.
In the conventional D-3 type VTR, the digital video and audio signals of one field interval are divided into three segments according to the NTSC 108 system or are divided into four segments according to the PAL 109 system, and then they are recorded sequentially on a magnetic tape having a width of 1/2 inch by a pair of magnetic heads with formation of inclined tracks on the magnetic tape 100. In this case, the recording areas of the digital audio signal are located at both ends of each inclined track in the inclined width direction as shown in FIG. 2. The audio channels 1 through 4, which is respectively shown by A1 through A4 in FIG. 2, are recorded dividedly in each field. The recording areas of the digital video and audio signals are segmented in the unit of a field so that the boundaries each between the respective adjacent segments or the respective adjacent fields coincide with the ends of each inclined track.
FIG. 3 shows a timing chart of signal processing in recording and reproducing a digital audio signal which is executed in the conventional D-3 type digital VTR according to PAL system. In FIG. 3, c represents the input video signal, a1 represents the input time interval of the recording audio signal, a2 represents the recording processing time interval of the digital audio signal, a3-a6 represent the recording time interval of the digital audio signal, b1-b4 represent the reproducing time interval of the digital audio signal, b5 represents the reproducing processing time interval of the digital audio signal, b6 represents the output time interval of the reproducing audio signal, e represents one segment, each f represents one field, and t represents increasing time.
Referring to FIG. 3, an inputted audio or speech signal of one field f interval is stored in advance of the top end of the video signal of one field interval by 128 samples as shown by a1 and h of FIG. 3. Taking advantage of the advance in time of the audio signal with respect to the video signal, digital audio signal recording processes including a shuffling process, an error correction code generating process and the like are executed every field as shown in a2 of FIG. 3. The audio signal is further divided into four segments as shown in a3 through a6 of FIG. 3, and then is recorded in both end portions of the inclined tracks.
In the reproducing stage, data of the four-channel digital audio signal of one field are inputted and stored in a field memory, and then digital audio signal recording processes including an error correction process, a deshuffling process and the like are executed and further outputting the resulting signal.
However, in executing a cross-fade editing process as an audio editing process by the conventional D-3 type digital VTR, it is required to output a reproduction audio signal in accordance with the same timing as the input timing for reproducing as shown in b6 of FIG. 3, so that the digital audio signal reproduced in a manner as shown in FIG. 3 can be recorded in the same position on the magnetic tape 100. For the above-mentioned reasons, the reproducing magnetic heads must be put in advance of the recording magnetic heads by 9.5 segments as shown by g in FIG. 3, with e representing one segment. Therefore, when achieving simultaneous reproduction and advanced reproduction by moving a set of movable magnetic heads, i.e., a set of so-called AT magnetic heads, it has been disadvantageously required to increase the quantity of movement of the AT magnetic heads.